In numerous signalling or lighting devices, and in particular in signalling lights, it is desirable to obtain a beam in which variations in light intensity from one point to another are as regular as possible.
In lighting devices that include a light-recovering mirror, it can be difficult to obtain such uniformity since it is observed, in particular, that certain points of the mirror can produce images of the light source that are extremely close to one another, thus giving rise to spots of concentrated light that are too marked.
A widely-known solution to that problem consists in providing prisms, beads, or stripes on the glass, globe, or front of the signalling or lighting device for the purpose of deflecting the light and in particular for dispersing excessively concentrated light, and correspondingly adding light in zones that are too dim.
Nevertheless, that solution is incompatible with the present trend of making such glasses, globes, or fronts as smooth as possible, in particular for reasons of appearance.
In this context, another solution that springs to the mind of the person skilled in the art consists in providing stripes, prisms, individual blocks, etc. on the mirror itself, so as to retain the predetermined beam outline while nevertheless ensuring greater uniformity of light within said outline.
Unfortunately, that solution complicates manufacture of the mirror and it also turns out to be unattractive in appearance since such light deflecting elements provided on the mirror when seen through the glass give the mirror an irregular appearance when the light is out.